TOP-electrode-eliminated organic bi-stable devices and their two switching modes in different atmospheres

J-V curves of ITO/NPB (60 nm)||NPB (60 nm)/ITO. Black square line shows the 1st scan from 18 V to −18 V and the red hollow circle line shows the 2nd scan from −18 V to 18 V. The conductance increases only when the bias polarity is reversed.